Commonly used as an abbreviated way to say "for
real".
Usually used in texting, as many
people use as many abbreviations as possible.
It can be a form of agreement towards someone, or disbelief.
If you use it as disbelief you
may put a question mark to emphasize that you're asking if they're being serious.
Friend 1: "yo dawg, my crush asked me out today!"
Friend
2: "fr?"
Ex.
2: )
Friend 1: "Damn it's cold outside, we might freeze to
death."
Friend 2: "yeah, fr."